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I have been looking up additional information and with the great discrepancy in cost of oil ($1.08 per litre) and the cost of gas ($0.09846 per cubic meter),this accounts for the cost difference between oil and gas heating. Just by switching fuel and using the same heating system would save me a great deal each year. The figures I got from the Cost Calculator at Natural Resources Canada concurs with yours, a one third savings.

dave sulz, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions to the OP here. Please apply to the AOPC today, thank you.

If you switch to a HIGH efficiency gas system I'd bet you get your money back on it in about five years, assuming that natural gas prices stay the same. And you would then only have a five year old heating system.

[B][I]"[COLOR=#000000][FONT=Verdana]A condensing boiler can have an AFUE rating of 90 percent or higher. But in practice, condensing boilers in hydronic (hot water) heating systems can have difficulty achieving this efficiency."

If you'll read the quote a little closer, you'll notice that it it doesn't say that a high efficiency boiler is a bad choice for high temp hydronics it says it "can have difficulty achieving" its efficiency rating. The reason for this is simple: the lower the return water temp to a mod/con, the higher its operating efficiency will be. If it's hooked to a high temp system where the return water temp is constantly above 140*, it won't be in its condensing mode and the efficiency will drop to about 88-90%. If the return water temp is below 110*, then its efficiency will be 97%+.

A mod/con comes with outdoor reset. This feature adjusts water temp to match the load: i.e. the warmer the outdoor temp, the lower the water temp. You only need 180* water when it's 0* outside. The Nation Resources statement doesn't account for this and is in that sense inaccurate about a mod/con. Outdoor reset allows the mod/con to run in condensing mode the majority of the heating season resulting in a boiler that's operating well above 90% most of the time.

Regarding your current boiler: it's doubtful that its efficiency was at 45% when it came out of the crate. And, that's a 1920's boiler. Someone may have brought it in from a previous house when yours was built. It's a gravity flow that may have been converted to forced flow. So is your system which is actually good news: they operate very efficiently with lower temps that mod/cons like vs. the higher temps required by baseboard.

Do yourself and your wallet a favor and install a good mod/con. I would not put a dime in what you've got.

Also, make sure you choose a good hydronics pro: that's far more important than the brand of boiler.

Bob Boan

​You can choose to do what you want, but you cannot choose the consequences. ​

My thought would be while changing to a conversion burner is an option, what happens to the investment when the boiler itself gives up the fight. If you like to gamble, then play the odds. At 60+ years, how long will she last? 10? More, less? Next week? When ever it craps out there goes your entire investment PLUS all of the operational cost savings you would have had with a new boiler. If you can swing a new boiler cost wise, do it. You won't be sorry.

Well, this thread has reach it's end, as has the aforementioned ARCO boiler. All that remains is the door, kept for sentimental reasons. For five days, now, a Viessmann Vitodens 100 is silently fulfilling the heating duties. I am happy so far. I'll be even happier when I don't have anymore outragous oil bills to pay. The real test comes in the dead of winter, but I have faith it will do it's job.
Thanks for all your suggestions and comments.
Over & Out!

It depends on how low you can set the outdoor reset curve. I live in NJ and my boiler water temp hasn't gone above 130 this winter. I had an old Am. Std 1951 boiler prior to my Triangle Tube boiler and my gas bill was reduced in half with the new unit. That is in therms, not dollars. I was used to $300 / mo gas bills my new one is only $100/ mo.